1. Field of the Invention
The present invention relates to butterfly valve devices for controlling the gas flow, and more particularly to valve devices that are formed by resin molding. These butterfly valve devices can be applied to, for example, a throttle valve device for controlling the airflow of an internal combustion engine.
2. Description of the Related Art
For a butterfly valve used for controlling the gas flow, typified by the airflow, the formation of the butterfly valve by resin molding is proposed from the viewpoint of the weight saving, and the formability. As an example, JP-A-2005-163546, JP-A-2005-180423, and JP-A-2005-273563 disclose that a throttle valve for controlling the airflow of an internal combustion engine is formed by resin molding.